Presentation on theme: "January 16, 2013Q-2 Pg. Daily Goal: We will be able to identify and explain 3 processes that shape the earth through weathering Homework: Turn in missing."— Presentation transcript:
January 16, 2013Q-2 Pg. Daily Goal: We will be able to identify and explain 3 processes that shape the earth through weathering Homework: Turn in missing work! Finish weathering packet Science Starter: 1.What type of rock is the Grand Canyon? 2.What do you think may have created the shape of the canyon?
In this PowerPoint, anytime that you see words written in purple, it means that you nee to write it down.
Weathering and Erosion ***Write this in your glossary*** Weathering: the breaking down of rocks into smaller pieces Erosion: the transport of sediment Both of these processes take a very long time to occur
The Effects of Weathering All exposed rock is in the path of weathering and erosion. Weathering is the process that breaks down rock and other substances at the Earth’s surface. Heat, cold, water, ice, carbon dioxide, oxygen etc.. all contribute to weathering.
Weathering and Erosion Weathering examples: –Repeated freezing and thawing. –Rainwater dissolving minerals. Weathering and erosion work together to carry away the rocks at the surface. There are two types of weathering: –Mechanical Weathering –Chemical Weathering
Mechanical Weathering Mechanical Weathering: when rock is physically broken into smaller pieces that have the same chemical composition as the rock they came from; changing a rock’s appearance –Examples: freezing and thawing, release of pressure, growth of plants, actions of animals, and abrasion (grinding away of rock by particles in the wind and water).
Weathering –Frost wedging: water freezes in cracks of the rocks and cracks the rock apart –Wind and water: break pieces of rock apart –Roots can break rocks apart too
Brain Boost! Frost wedging occurs when water collects in cracks or openings in rock, then freezes and expands. This expansion of the water can force the rock to split. This is an example of what kind of weathering? A.Thermal B.Chemical C.Biological D.Mechanical
Weathering Chemical Weathering: chemically changing the rocks to break them down
Chemical Weathering Chemical Weathering: the process that breaks down rock through chemical changes and produces rock particles that have a different mineral makeup from the rock they came from. –Examples: Hot or soft spots in rock Water Oxygen Carbon Dioxide Living organisms Acid Rain
Water Water weathers rock by dissolving the minerals in it.
Oxygen Iron combines with oxygen in the presence of water in a processes called oxidation The product of oxidation is rust.
This rock in Utah is red because of the oxidation of iron in the sediment when the rock was being formed.
Carbon Dioxide CO 2 dissolves in rain water and creates carbonic acid. Carbonic acid easily weathers limestone and marble.
Living Organisms The roots of Lichens that grow on rocks produce weak acids that chemically weather rock
Acid Rain Compounds from burning fossil fuels (coal, oil and gas) react chemically with rain water and forms acids. Acid rain causes very rapid chemical weathering.
1908 to 1969 Acid rain has eaten away this limestone statue.
Rate of Weathering The most important factors that determine the rate at which weathering occurs are the type of rock and climate. Type of Rock –Minerals will determine the rate. –Permeable rocks (full of tiny air spaces) weather faster. Climate: –Weathering occurs faster in wet climates and higher temperatures.
Brain Break: Take one minute to answer this question: –Think about when we dissolved a piece of chalk in vinegar. Was that an example of physical or chemical weathering? List at least 2 reasons that support your answer. I will stamp completed work.
EXIT TICKET Let’s revisit our answers. Answer these questions again using what yo u learned. 1.What type of rock is the Grand Canyon? 2.What do you think may have created the shape and color of the canyon?
Soil Formation Over many years, weathering and erosion will cause the formation of soil. Soil is the loose, weathered material on the Earth’s surface in which plants can grow. Soil forms as rock is broken down by weathering and mixes with other materials on the surface.
Soil Composition Soil is constantly being formed wherever bedrock is exposed. –Bedrock is the solid layer of rock beneath the soil. Soil is a mixture of rock particles, minerals, decayed organic material, air, and water.
Soil Composition and Texture The decayed organic material in the soil is humus. –Humus is a dark-colored substance that forms as plant and animal remains decay. Soil texture depends on the size of individual soil particles. –Soil texture is important for plant growth.
Soil Horizons A soil horizon is a layer of soil that differs in color and texture from the layers above or below it. –Topsoil (A horizon) is a crumbly, dark brown soil that is a mixture of humus, clay, and other materials. –Subsoil (B horizon) usually consists of clay, and other particles washed down from the topsoil, but little humus. –C horizon contains only partly weathered rock.
Life in Soil Some organisms mix the soil and make spaces in it for air and water. Other soil organisms make humus, the material that makes soil fertile. –Humus forms through decomposition. –Fertile soil is rich in nutrients that plants need. As plants shed leaves, they form a loose layer called litter.
Soil Types in the U.S. Tundra Soils Northern Forest Soils Prairie Soils Mountain Soils Southern Forest Soils Desert Soils Tropical Soils
Soil Conservation Soil is one of Earth’s most valuable resources because everything that lives on the land depends directly on indirectly on soil. Fertile soil is valuable because there is a limited supply. –Less than 1/8 th of the land on Earth has soils well suited for farming.
Soil Damage and Loss Soil can become exhausted, or lose its fertility. Soil can also become lost to erosion by water and wind. –Water erosion can occur wherever soil is not protected by plant cover. –Wind erosion caused the Great Dust Bowl!!
The Dust Bowl In the 1930s plowing removed the grass form the Great Plains and exposed the soil. In times of drought, the topsoil quickly dried out, turned to dust, and blew away. This event helped people appreciate the value of soil. Check It Out!!
Soil Conservation Soil Conservation is the management of soil to prevent its destruction. Two ways that soil can be conserved include contour plowing and conservation plowing.
Contour Plowing Contour plowing is the practice of plowing fields along the contours of a slope. This helps slow the runoff of excess rainfall and prevents it from washing the soil away.
Conservation Plowing Conservation Plowing disturbs the soil and its plant cover as little as possible. Dead weeds and stalks of the previous year’s crop are left in the ground to help return soil nutrients.
Erosion Erosion reshapes earth’s surface by moving sediment What moves the sediment? –Water –Wind Erosion is highest in areas with no vegetation
How do we prevent erosion? Create a windbreak by planting a row of trees Strip farming: alternating crop types to help hold the soil in place Contour farming: farmers plow at right angles to the slope of a hill. This keeps the soil from washing away
Sample Question… A farmer is concerned about the erosion of his soil by the action of the wind. Which would be the best way for the farmer to reduce wind erosion? A.Add worms to the soil so that the drainage improves B.Fertilize the soil so that plants have more nutrients C.Plant a row of trees that act as a wind break D.Water the soil less often so that the soil dries out